The invention relates to a disposable injector with a housing, in which or on which—respectively at least in certain areas—at least one mechanical spring-energy storage, at least one cylinder-piston unit which can be filled at least occasionally with active ingredient, at least one piston-actuating plunger and at least one actuating unit are arranged, whereby the spring-energy storage includes at least one pre-stressed spring-loaded element, whereby at least part of the piston-actuating plunger is positioned between the spring-energy storage and the piston of the cylinder-piston unit and whereby the piston of the cylinder-piston unit—with a prestressed spring element—can be moved separately via a pump rod.
US 2001/0051789 A1 discloses inter alia such an injector which has a spring pre-stressed piston-actuating plunger which, upon actuation of the injector, acts on a rigid combination of piston and piston rod of the piston guided in the cylinder-piston unit. The one-piece piston rod is continued rearwards so far that its protrudes beyond the rear housing end of the injector. By means of the rear end of the piston rod, the piston can be moved separately by hand. The interior of the cylinder of the cylinder-piston unit cannot be closed off here in a sterile manner, and the entire piston rod is moved during the injection.
The present invention therefore addresses the problem of developing a modular disposable injector the cylinder-piston unit of which is able to be filled in the assembled state. This injector has only a few components for its minimal structural size and guarantees secure mounting and function with easy handling. The injection solution can be kept sterile for up to two years, even in the manually filled injector.
The object of the present invention is to provide a pump rod that can be coupled releasably to the piston or to a piston rod of the piston. The cylinder of the cylinder-piston unit has a rear sealing element that permits sterile closure of the cylinder interior located between the piston and the cylinder.